(SPOJ) 11647 - Overflow - Solução

import java.io.*;
import java.util.*;

class Main {
    public static void main(String[] args) throws NumberFormatException, IOException {
        Main processando = new Main();
        processando.processa();
       
        System.exit(0);
    }
   
    void processa() throws NumberFormatException, IOException {
        String line = "";
       
        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));

        line = br.readLine();
        StringTokenizer tokenizer = new StringTokenizer(line);
        int valor = Integer.valueOf(tokenizer.nextToken());
           
        boolean segundo = false;
        boolean operador = false;
        String a = "";
        String b = "";
        char op = '+';
        line = br.readLine();
        for (int i = 0; i < line.length(); i++) {
            if (line.charAt(i) == ' ' && segundo == false) {
                operador = true;
            }
            if (!operador && !segundo) {
                a += line.charAt(i);
            }
            else if (operador) {
                if (line.charAt(i) != ' ') {
                    op = line.charAt(i);
                    segundo = true;
                    operador = false;
                }
            }
            else if (segundo) {
                if (line.charAt(i) != ' ') {
                    b += line.charAt(i);
                }
            }
        }
       
        int a1 = Integer.parseInt(a);
        int b1 = Integer.parseInt(b);
        if (op == '*') {
            if ((a1*b1) <= valor) {
                System.out.println("OK");
            }
            else {
                System.out.println("OVERFLOW");
            }
        }
        else {
            if ((a1+b1) <= valor) {
                System.out.println("OK");
            }
            else {
                System.out.println("OVERFLOW");
            }
        }
                                   
        return;
    }
}